Mistakes in paying sickness benefits are likely to have affected more than 8,000 claimants in Northern Ireland, a Stormont department has said.
The figure was revealed after a query from SDLP MLA Nichola Mallon, who said those affected have been underpaid by an average of about £3,000 each.
The error, which applies to Employment and Support Allowance, was identified in an Audit Office report last month.
Ms Mallon said there was no question it "forced people further into poverty".
"The fact that some 8,000 ESA claimants here have been underpaid an average of £3,000 each as a result of another benefit blunder is scandalous," she said.
"The fact that this shocking information has only come to light after the SDLP pursued the matter is also concerning."
Last month, a report from the National Audit Office stated that the Department for Work and Pensions "has underpaid an estimated 70,000 people" in the UK who were in receipt of Employment and Support Allowance (ESA) since 2011.
Following that publication, Ms Mallon wrote to Stormont's Department for Communities to ask if claimants in Northern Ireland had been affected by the mistake.
On Thursday, a spokeswoman for the Department for Communities confirmed they had established that "just over 8,000 Northern Ireland claimants may be affected".
Ms Mallon called on the department to "set out clearly how and when those affected will be paid what they are owed".
"The lives of vulnerable claimants are tough enough without being denied the support they are entitled to for seven years," the MLA added.
The Department for Communities has confirmed that it will make direct contact with all claimants affected by the error.
"In line with the Department for Work and Pensions approach, we will aim to complete a review of all affected cases by April 2019," the spokeswoman added.
Employment and Support Allowance was introduced in the UK by the Labour government in 2008 to replace incapacity benefit.
It is paid to benefits claimants with long-term chronic health conditions.